The nature and significance of public exposure to arsenic: a review of its relevance to South West England

Arsenic in residential soil and household dust in Cornwall, south west England: potential human exposure and the influence of historical mining

Exposure to arsenic (As) via residential soil and dust is a global concern, in regions affected by mining or with elevated concentrations present in underlying geology. Cornwall in south west England is one such area. Residential soil (n = 127) and household dust (n = 99) samples were collected from across Cornwall as part of a wider study assessing exposure to environmental As. Samples were analysed for total As (soil and dust samples) and human ingestion bioaccessible As (soil samples from properties with home-grown produce). Arsenic concentrations ranged from 12 to 992 mg kg^-1 in soil and 3 to 1079 mg kg^-1 in dust and were significantly higher in areas affected by metalliferous mineralisation. Sixty-nine percent of soils exceeded the 37 mg kg^-1 Category 4 Screening Level (C4SL), a generic assessment criteria for As in residential soils in England, which assumes 100% bioavailability following ingestion. The proportion of exceedance was reduced to 13% when the bioavailability parameter in the CLEA model was changed to generate household specific bioaccessibility adjusted assessment criteria (ACBIO). These criteria were derived using bioaccessibility data for a sub-set of individual household vegetable patch soils (n = 68). Proximity to former As mining locations was found to be a significant predictor of soil As concentration. This study highlights the value of bioaccessibility measurements and their potential for adjusting generic assessment criteria.

Arsenic accumulation in rice: Consequences of rice genotypes and management practices to reduce human health risk

Rice is an essential staple food and feeds over half of the world's population. Consumption of rice has increased from limited intake in Western countries some 50years ago to major dietary intake now. Rice consumption represents a major route for inorganic arsenic (As) exposure in many countries, especially for people with a large proportion of rice in their daily diet as much as 60%. Rice plants are more efficient in assimilating As into its grains than other cereal crops and the accumulation may also adversely affect the quality of rice and their nutrition. Rice is generally grown as a lowland crop in flooded soils under reducing conditions. Under these conditions the bioavailability of As is greatly enhanced leading to excessive As bioaccumulation compared to that under oxidizing upland conditions. Inorganic As species are carcinogenic to humans and even at low levels in the diet pose a considerable risk to humans. There is a substantial genetic variation among the rice genotypes in grain-As accumulation as well as speciation. Identifying the extent of genetic variation in grain-As concentration and speciation of As compounds are crucial to determining the rice varieties which accumulate low inorganic As. Varietal selection, irrigation water management, use of fertilizer and soil amendments, cooking practices etc. play a vital role in reducing As exposure from rice grains. In the meantime assessing the bioavailability of As from rice is crucial to understanding human health exposure and reducing the risk.

Prolonged exposure to arsenic in UK private water supplies: toenail, hair and drinking water concentrations

Chronic exposure to arsenic (As) in drinking water is an established cause of cancer and other adverse health effects. Arsenic concentrations >10 μg L(-1) were previously measured in 5% of private water supplies (PWS) in Cornwall, UK. The present study investigated prolongued exposure to As by measuring biomarkers in hair and toenail samples from 212 volunteers and repeated measurements of As in drinking water from 127 households served by PWS. Strong positive Pearson correlations (rp = 0.95) indicated stability of water As concentrations over the time period investigated (up to 31 months). Drinking water As concentrations were positively correlated with toenail (rp = 0.53) and hair (rp = 0.38) As concentrations - indicative of prolonged exposure. Analysis of washing procedure solutions provided strong evidence of the effective removal of exogenous As from toenail samples. Significantly higher As concentrations were measured in hair samples from males and smokers and As concentrations in toenails were negatively associated with age. A positive association between seafood consumption and toenail As and a negative association between home-grown vegetable consumption and hair As was observed for volunteers exposed to <1 As μg L(-1) in drinking water. These findings have important implications regarding the interpretation of toenail and hair biomarkers. Substantial variation in biomarker As concentrations remained unaccounted for, with soil and dust exposure as possible explanations.

Urinary arsenic profiles reveal exposures to inorganic arsenic from private drinking water supplies in Cornwall, UK

Private water supplies (PWS) in Cornwall, South West England exceeded the current WHO guidance value and UK prescribed concentration or value (PCV) for arsenic of 10 μg/L in 5% of properties surveyed (n = 497). In this follow-up study, the first of its kind in the UK, volunteers (n = 207) from 127 households who used their PWS for drinking, provided urine and drinking water samples for total As determination by inductively coupled plasma mass spectrometry (ICP-MS) and urinary As speciation by high performance liquid chromatography ICP-MS (HPLC-ICP-MS). Arsenic concentrations exceeding 10 μg/L were found in the PWS of 10% of the volunteers. Unadjusted total urinary As concentrations were poorly correlated (Spearman's ρ = 0.36 (P < 0.001)) with PWS As largely due to the use of spot urine samples and the dominance of arsenobetaine (AB) from seafood sources. However, the osmolality adjusted sum, U-As(IMM), of urinary inorganic As species, arsenite (As(III)) and arsenate (As(V)), and their metabolites, methylarsonate (MA) and dimethylarsinate (DMA), was found to strongly correlate (Spearman's ρ: 0.62 (P < 0.001)) with PWS As, indicating private water supplies as the dominant source of inorganic As exposure in the study population of PWS users.

Impact assessment of mercury accumulation and biochemical and molecular response of Mentha arvensis: a potential hyperaccumulator plant

The present study was focused on examining the effect of Hg oxidative stress induced physiochemical and genetic changes in M. arvensis seedlings. The growth rate of Hg treated seedlings was decreased to 56.1% and 41.5% in roots and shoots, respectively, compared to the control. Accumulation of Hg level in both roots and shoots was increased with increasing the concentration of Hg. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were found to be increased with increasing the Hg concentration up to 20 mg/L; however, it was decreased at 25 mg/L Hg concentration. The POX enzyme activity was positively correlated with Hg dose. The changes occurring in the random amplification of ploymorphic DNA (RAPD) profiles generated from Hg treated seedlings included variations in band intensity, disappearance of bands, and appearance of new bands compared with the control seedlings. It was concluded that DNA polymorphisms observed with RAPD profile could be used as molecular marker for the evaluation of heavy metal induced genotoxic effects in plant species. The present results strongly suggested that Mentha arvensis could be used as a potential phytoremediator plant in mercury polluted environment.

Fractionation and speciation of arsenic in fresh and combusted coal wastes from Yangquan, northern China

In this study, the content and speciation of arsenic in coal waste and gas condensates from coal waste fires were investigated, respectively, using the digestion and sequential extraction methods. The fresh and fired-coal waste samples were collected from Yangquan, which is one of the major coal production regions in northern China. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) was used to determine the concentrations of four major arsenic species [As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA)] in the extracts, while ICP-MS was used to measure total As content. Arsenic content in the investigated coal wastes and the condensate ranges between 23.3 and 69.3 mg/kg, which are higher than its reported average content in soils. Arsenic in coal waste exists primarily in the residual fraction; this is followed in decreasing order by the organic matter-bound, Fe-Mn oxides-bound, exchangeable, carbonates-bound, and water-soluble fractions. The high content of arsenic in the condensates indicates that combustion or spontaneous combustion is one of the major ways for arsenic release into the environment from coal waste. About 15% of the arsenic in the condensate sample is labile and can release into the environment under leaching processes. The water extractable arsenic (WEA) in the fresh coal waste, fired coal wastes, and the condensate varied between 14.6 and 341 μg/kg, with As(V) as the major species. Furthermore, both MMA and DMA were found in fresh coal wastes, fired coal wastes, and the condensate.

Determination of As(III) by anodic stripping voltammetry using a lateral gold electrode: experimental conditions, electron transfer and monitoring of electrode surface

The aim of this work is to evaluate the efficiency of the determination of As(III) by anodic stripping voltammetry (ASV) using a lateral gold electrode and to study the modifications of the electrode surface during use. Potential waveforms (differential pulse and square wave), potential scan parameters, deposition time, deposition potential and surface cleaning procedure were examined for they effect on arsenic peak intensity and shape. The best responses were obtained with differential pulse potential wave form and diluted 0.25 M HCl as supporting electrolyte. The repeatability, linearity, accuracy and detection limit of the procedure and the interferences of cations and anions in solution were evaluated. The applicability of the procedure for As(III) determination in drinking waters was tested. Cyclic voltammetry (CV) was used to study the electrochemical behaviour of As(III) and for the daily monitoring of electrode surface. Also scanning electron microscopy (SEM) analysis was used to control the electron surface. Finally we evaluated the possibility to apply the equations valid for flow systems also to a stirred system, in order to calculate the number of electrons transferred per molecule during the stripping step.

Arsenic stability and mobilization in soil at an amenity grassland overlying chemical waste (St. Helens, UK)

A 6.6 ha grassland, established on a former chemical waste site adjacent to a residential area, contains arsenic (As) in surface soil at concentrations 200 times higher than UK Soil Guideline Values. The site is not recognized as statutory contaminated land, partly on the assumption that mobility of the metalloid presents a negligible threat to human health, groundwater and ecological receptors. Evidence for this is evaluated, based on studies of the effect of organic (green waste compost) and inorganic (iron oxides, lime and phosphate) amendments on As fractionation, mobility, plant uptake and earthworm communities. Arsenic mobility in soil was low but significantly related to dissolved organic matter and phosphate, with immobilization associated with iron oxides. Plant uptake was low and there was little apparent impact on earthworms. The existing vegetation cover reduces re-entrainment of dust-blown particulates and pathways of As exposure via this route. Minimizing risks to receptors requires avoidance of soil exposure, and no compost or phosphate application.

Arsenite oxidation by immobilized cells of Alcaligenes faecalis strain O1201 in a fluidized-bed reactor

Arsenic(III) oxidation was evaluated in a continuous-flow fluidized-bed reactor (FBR) with Alcaligenes faecalis strain 01201 immobilized in gel beads. The FBR was operated under 300 mg/L citrate and a range of influent As(III) concentrations (75 to 3000 mg/L) at short hydraulic retention times (1.06 to 3.17 hours). The pH and temperature in the FBR were maintained at optimal growth conditions for strain O1201 (pH 7 and 30 degrees C) throughout the study. A total of 10 quasi-steady-state operating conditions were obtained after 54 days of operation under an As(III) concentration of 441 mg/L (10 000 mg/L/d loading rate), with As (III) removal efficiency ranging from 76% to near complete. Material balance analysis over the FBR revealed that the difference between the cumulative influent As (III) and the sum of cumulative effluent As(III) and As(V) was insignificant. The major mechanism of As(III) removal from the FBR is biological oxidation to As(V).

Effect of in situ soil amendments on arsenic uptake in successive harvests of ryegrass (Lolium perenne cv Elka) grown in amended As-polluted soils

Several iron-bearing additives, selected for their potential ability to adsorb anions, were evaluated for their effectiveness in attenuation of arsenic (As) in three soils with different sources of contamination. Amendments used were lime, goethite (alpha-FeOOH) (crystallised iron oxide) and three iron-bearing additives, iron grit, Fe(II) and Fe(III) sulphates plus lime, applied at 1% w/w. Sequential extraction schemes conducted on amended soils determined As, Cu, Zn and Ni fractionation. Plant growth trials using perennial ryegrass (Lolium perenne var. Elka) assessed shoot As uptake. This was grown in the contaminated soils for 4 months, during which time grass shoots were successively harvested every 3 weeks. Goethite increased biomass yields, but clear differences were observed in As transfer rates with the various iron oxides. In conclusion, whilst Fe-oxides may be effective in situ amendments, reducing As bioavailability, their effects on plant growth require careful consideration. Soil-plant transfer of As was not completely halted by any amendment.

Arsenic in soils and plants of woodland regenerated on an arsenic-contaminated substrate: a sustainable natural remediation?

Plant As accumulation at three As-polluted sites where spontaneous re-vegetation has taken place is examined. Each site had a different source of soil As (coal fly ash, LeBlanc process waste, canal dredging). Plant analysis indicates that soil-plant As transfer is poor at each site. Any mobile As is retained in root tissues, with little transfer to shoots. Bryophytes, pteridophytes, herbaceous and woody plants sampled at each site predominantly showed As concentrations of <3 mg kg(-1) dry wt, whilst total soil As ranged between 50 and 220 mg kg(-1) dry wt. Risk associated with food chain transfer at these sites is low when compared to other routes such as direct ingestion/inhalation of As-contaminated particulates re-entrained from an unvegetated or unstable substrate.

Effects of arsenic on seed germination and physiological activities of wheat seedlings

The effects of arsenic (As) were investigated on seed germination, root and shoot length and their biomass and some other factors to elucidate the toxicity of As. The results showed low concentrations of As (0-1 mg/kg) stimulated seed germination and the growth of root and shoot, however, these factors all decreased gradually at high concentrations of As (5-20 mg/kg). The contents of O2*-, MDA, soluble protein and peroxidase (POD) activity all increased with increasing As concentrations. Soluble sugar content, ascorbate peroxidase (APX), and superoxide dismutase (SOD) activities decreased at low concentrations of As, and increased at high concentrations of As. While acetylsalicylic acid (ASA) and chlorophyll contents, catalase (CAT) activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg, and then decreasing trend. By polyacrylamide gel electrophoresis (PAGE), As induced the expression of POD isozymes of wheat seedlings. As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg. However, As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg. The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.

Bioaccessible arsenic in the home environment in southwest England

Samples of household dust and garden soil were collected from twenty households in the vicinity of an ex-mining site in southwest England and from nine households in a control village. All samples were analysed by ICP-MS for pseudo-total arsenic (As) concentrations and the results show clearly elevated levels, with maximum As concentrations of 486 microg g(-1) in housedusts and 471 microg g(-1) in garden soils (and mean concentrations of 149 microg g(-1) and 262 microg g(-1), respectively). Arsenic concentrations in all samples from the mining area exceeded the UK Soil Guideline Value (SGV) of 20 microg g(-1). No significant correlation was observed between garden soil and housedust As concentrations. Bioaccessible As concentrations were determined in a small subset of samples using the Physiologically Based Extraction Test (PBET). For the stomach phase of the PBET, bioaccessibility percentages of 10-20% were generally recorded. Higher percentages (generally 30-45%) were recorded in the intestine phases with a maximum value (for one of the housedusts) of 59%. Data from the mining area were used, together with default values for soil ingestion rates and infant body weights from the Contaminated Land Exposure Assessment (CLEA) model, to derive estimates of As intake for infants and small children (0-6 years old). Dose estimates of up to 3.53 microg kg(-1) bw day(-1) for housedusts and 2.43 microg kg(-1) bw day(-1) for garden soils were calculated, compared to the index dose used for the derivation of the SGV of 0.3 microg kg(-1) bw day(-1) (based on health risk assessments). The index dose was exceeded by 75% (18 out of 24) of the estimated As doses that were calculated for children aged 0-6 years, a group which is particularly at risk from exposure via soil and dust ingestion. The results of the present study support the concerns expressed by previous authors about the significant As contamination in southwest England and the potential implications for human health.

Soil As contamination and its risk assessment in areas near the industrial districts of Chenzhou City, Southern China

In order to assess soil As contamination and potential risk for human, soil, paddy rice, vegetable and human hair samples from the areas near the industrial districts in Chenzhou, southern China were sampled and analyzed. The results showed that the anthropogenic industrial activities have caused in local agricultural soils to be contaminated with As in a range of 11.0-1217 mg/kg. The GIS-based map shows that soil contamination with As occurred on a large scale, which probably accounted for up to 30% of the total area investigated. Soil As concentration abruptly decreased with an increase in the distance from the polluting source. High As concentrations were found in the rice grain that ranged from 0.5 to 7.5 mg/kg, most of which exceed the maximal permissible limit of 1.0 mg/kg dry matter. Arsenic accumulated in significantly different levels between leafy vegetables and non-leafy vegetables. Non-leafy vegetables should be recommended in As-contaminated soils, as their edible parts were found in relatively low As level. Arsenic concentrations in 95% of the total human hair samples in the contaminated districts were above the critical value, 1.0 mg/kg, set by the World Health Organization. Arsenic could be enriched in human hair to very high levels without being affected by As containing water. The results revealed that the soils and plants grown on them are major contributors to elevate hair As in the industrial population. Therefore, the potential impact on human health of ingestion/inhalation of soil As around the industrial districts seems to be rather serious. Hence proper treatments for As contaminated soils are urgently needed to reduce the contamination.

Arsenic availability from chromated copper arsenate (CCA)-treated wood

Lumber used to construct raised garden beds is often treated with chromated copper arsenate (CCA). This project aimed to determine (i) how far As, Cu, and Cr had diffused away from CCA-treated wood surfaces in raised garden beds under realistic conditions, (ii) the uptake of these elements by crops, and (iii) the effect of CCA solution on soil bacteria. This study showed that As, Cu, and Cr diffuse into soil from CCA-treated wood used to construct raised garden beds. To determine crop uptake of these elements, contaminated soil 0 to 2 cm from the treated wood was obtained from two different beds (40-50 mg kg(-1) As); control soil was collected 1.5 m away from the treated wood (<3-10 mg kg(-1) As). Four replicates of carrot (Daucus carota var. sativus Hoffm. cv. Thumbelina), spinach (Spinacia oleracea L. cv. Indian Summer), bush bean (Phaseolus vulgaris L. cv. Provider), and buckwheat (Fagopyrum esculentum Moench cv. Common) were grown in pots containing these soils in a greenhouse. After harvest, plant materials were dried, ground, digested, and analyzed for As by inductively coupled plasma-hydride generation (ICP-HG). Concentrations of As in all crops grown in contaminated soils were higher than those from control soils. The levels of As in the crops remained well below the recommended limit for As set by the United States Public Health Service (2.6 mg kg(-1) fresh wt.). To determine if bacteria in soils 0 to 2 cm from the treated wood had higher resistance to Type C chromated copper arsenate (CCA-C) solution than those from reference soils, dilution plates were set up using quarter-strength tryptic soy agar (TSA) media and 0 to 22.94 g L(-1) (0-1.25% v/v) CCA-C working solution. The microorganisms from soils adjacent to treated wood had greater growth on the CCA-amended media than those from reference soils outside the bed.

Field trials to assess the uptake of arsenic by vegetables from contaminated soils and soil remediation with iron oxides

The uptake of arsenic (As) by plants from contaminated soils presents a health hazard that may affect the use of agricultural and former industrial land. Methods for limiting the hazard are desirable. A proposed remediation treatment comprises the precipitation of iron (Fe) oxides in the contaminated soil by adding ferrous sulfate and lime. The effects on As bioavailability were assessed using a range of vegetable crops grown in the field. Four UK locations were used, where soil was contaminated by As from different sources. At the most contaminated site, a clay loam containing a mean of 748 mg As kg(-1) soil, beetroot, calabrese, cauliflower, lettuce, potato, radish and spinach were grown. For all crops except spinach, ferrous sulfate treatment caused a significant reduction in the bioavailability of As in some part of the crop. Application of ferrous sulfate in solution, providing 0.2% Fe oxides in the soil (0-10 cm), reduced As uptake by a mean of 22%. Solid ferrous sulfate was applied to give concentrations of 0.5% and 1% Fe oxides: the 0.5% concentration reduced As uptake by a mean of 32% and the 1% concentration gave no significant additional benefit. On a sandy loam containing 65 mg As kg(-1) soil, there was tentative evidence that ferrous sulfate treatment up to 2% Fe oxides caused a significant reduction in lettuce As, but calabrese did not respond. At the other two sites, the effects of ferrous sulfate treatment were not significant, but the uptake of soil As was low in treated and untreated soils. Differences between sites in the bioavailable fraction of soil As may be related to the soil texture or the source of As. The highest bioavailability was found on the soil which had been contaminated by aerial deposition and had a high sand content.

Soils: their implications to human health

This paper reviews how the health of humans is affected by the world's soils, an association that to date has been under appreciated and under reported. Soils significantly influence a variety of functions (e.g. as a plant growth medium; its importance on the cycling of water; as a foundation for buildings) that sustains the human population. Through ingestion (either deliberate or involuntary), inhalation and dermal absorption, the mineral, chemical and biological components of soils can either be directly beneficial or detrimental to human health. Specific examples include: geohelminth infection and the supply of mineral nutrients and potentially harmful elements (PHEs) via soil ingestion; cancers caused by the inhalation of fibrous minerals or Rn gas derived from the radioactive decay of U and Th in soil minerals; and tetanus, hookworm disease and podoconiosis caused by skin contact and dermal absorption of appropriate soil constituents. Human health can also be influenced in more indirect ways as soils interact with the atmosphere, biosphere and hydrosphere. Examples include: the volatilisation of persistent organic pollutants (POPs) from soils and their subsequent global redistribution that has health implications to the Aboriginal people of the Arctic; the frequent detrimental chemical and biological quality of drinking and recreational waters that are influenced by processes of soil erosion, surface runoff, interflow and leaching; and the transfer of mineral nutrients and PHEs from soils into the plants and animals that constitute the human food chain. The scale and magnitude of soil/health interactions are variable, but at times a considerable number of people can be affected as demonstrated by the extent of hookworm infection or the number of people at risk because they live in an I-deficient environment. Nevertheless, it can often be difficult to establish definite links between soils and human health. This, together with the emergence of new risks, knowledge, or discoveries, means that there is considerable scope for research in the future. Such investigations should involve a multidisciplinary approach that both acquires knowledge and ensures its dissemination to people in an understandable way. This requires an infrastructure and finance that governments need to be responsive to.

Methylarsonic and dimethylarsinic acids toxicity and total arsenic accumulation in edible bush beans, Phaseolus vulgaris

The main objective was to evaluate whether arsenic accumulated in the edible pods and seeds of Phaseolus vulgaris, cv. F15 above the Spanish maximum recommended concentration for food crops, 1 mg kg(-1) on a fresh weight basis. Only organic arsenicals, methylarsonic and dimethylarsinic acids were used because they were: (1) the only arsenic species allowed for agricultural applications and (2) more mobile than inorganic species. Selection of French beans, a sensitive plant to arsenic, was based on the fact that arsenic-upward translocation is higher in sensitive than in tolerant plants. A 2 x 3 factorial experiment was conducted with two organic arsenic species (methylarsonic acid, dimethylarsinic acid) and three arsenic concentrations (0.2, 0.5, 1.0 mg l(-1)). Experimental results showed that the low bean plant tolerance to arsenic was possibly due to the high arsenic-upward transport to shoots, which could result in profound negative metabolic consequences. Even under extreme adverse conditions, arsenic residues in edible beans were below the maximum statutory limit set by the Spanish legislation. It is concluded that the major drawback of organic arsenical herbicides is that of decreased productivity rather than high arsenic intake by consumers of edible products from sensitive plant species.

Total arsenic accumulation in edible pods and seeds of Phaseolus vulgaris

The main objective of this study was to evaluate whether arsenic accumulated in the edible pods and seeds of Phaseolus vulgaris, cv. Helda, above the Spanish maximum recommended concentration for food crops, 1 mg kg(-1) on a fresh weight basis. Only organic arsenicals were used because they are: a) the only arsenic species allowed for agricultural applications and b) more mobile than inorganic species. Selection of French beans, a sensitive plant to arsenic, was based on the fact that arsenic upward translocation is higher in sensitive than in tolerant plants. A 2 x 3 factorial experiment was conducted with two organic arsenic species: methylarsonic acid (MAA) or dimethylarsinic acid (DMAA) and three arsenic concentrations: 0.2, 0.5, or 1.0 mg L(-1). Arsenic phytotoxicity was primarily determined by soluble arsenic concentration. Experimental results showed that the low bean plant tolerance to arsenic is possibly due to the high arsenic upward transport to shoots, which could result in profound negative metabolic consequences. Even under extremely adverse conditions, arsenic residues in edible beans were below the maximum statutory limit set by the Spanish legislation. It can be concluded that the major danger of organic arsenical herbicides is that of decreased productivity rather than high arsenic uptake by consumers.

On-site analysis of arsenic in groundwater using a microfabricated gold ultramicroelectrode array

Rapid on-site analysis of arsenic in groundwater was achieved with a small battery-powered unit in conjunction with a microfabricated gold ultramicroelectrode array (Au-UMEA). The sensor, consisting of 564 UME disks with a unique gold surface created by electron beam evaporation, was demonstrated to be highly sensitive to low-ppb As3+ using square wave anodic stripping voltammetry. The influence of the square wave frequency, pulse amplitude, and deposition potential on the arsenic peak stripping current was investigated. Varying those theoretical parameters yielded results surprisingly similar to those for the thin Hg film case. The performance of the Au-UMEA was evaluated for reproducibility and reliability. Three stability tests showed an average relative standard deviation of 2.5% for 15 consecutive runs. Limits of detection were investigated, and 0.05 ppb As3+ could be measured while maintaining a S/N of 3:1. Interference studies were performed in the presence of 50-500 ppb of Cu2+, Hg2+, and Pb2+. On-site analysis of groundwater containing arsenic was performed with a small battery-powered potentiostat. Quantification was done through standard additions, and these results were compared to the standard EPA methodology.

Transfer of cadmium, lead, and zinc from industrially contaminated soil to crop plants: a field study

The documeneed adverse health effects of soil Cd and Pb have led to public concern over soil contamination with metals. A 4-year field experiment was conducted to study the transfer of Cd, Pb, and Zn from soil contaminated by smelter flue-dust to crop plants grown in a rotation. The soil was amended with Pb?Zn smelter flue-dust (2-66.8 kg per 10 m(2) plot) to simulate the long-term effect that the smelting of non-ferrous metal ore has on arable soils. The treated soil became strongly contaminated with metals (Cd 3.2-106 mg/kg, Pb 146-3452 mg/kg, Zn 465-11 375 mg/kg). Concentrations of Cd, Pb, and Zn in barley grain, barley straw meadow bluegrass, red clover, and potatoes were generally low. The highest metal concentrations were found in potato tubers (intact), meadow bluegrass, and barley straw. The observed reduction in crop yield was probably the result of possible nutrient imbalances rather than of metal (Zn, Cu) phytotoxicities. Zn and Cd uptake by the plants can be described by the saturation (plateau) model (y = ax(b), b < 1). The relationship between Pb in the soil and plants was linear with an extremely low slope (0.0001-0.0003). No excessive dietary intake of Cd is expected when Cd concentrations in barley grain and potato tubers grown on the contaminated soil are not higher than 0.6 and 1.0 mg/kg, respectively. Based on the risk analysis and taking into account the saturation model of the soil-plant metal relationship, it was concluded that, under the conditions of this experiment (neutral soil pH), soil with Cd concentrations of up to 30 mg/kg is still safe for production of these crop plants.